Electrolysis Flashcards
What is electrolysis?
The separation of substances into their elements using electricity.
What happens in electrolysis?
An electric current is passed through an electrolyte (a molten or dissolved ionic compound) causing it to decompose
Where do the positive ions (cations) in the electrolyte move towards?
The cathode (negative electrode) and are reduced so they gain electrons
Where do the negative ions (anions) in the electrolyte move towards?
The anode (positive electrode) and are oxidised so they lose electrons
What is an electrolyte?
Ionic compounds with freely moving ions and can conduct electricity. In the molten state or dissolved in water.
What is the acronym about the electrodes?
PANIC. Positive anode negative is cathode
What is oxidation?
Loss of electrons
What is reduction?
Gain of electrons
What do substances have to be in electrolysis?
Have to be a liquid either molten or in solution this means the ions are free to move.
What are the two types of electrodes?
Inert carbon (can’t react). Copper electrodes (usually used with a copper solution)
Electrolysis core practical.
Measure mass of copper electrodes at start.
Carry out electrolysis.
Measure mass of copper electrodes at end.
What is the negative electrode?
Cathode. Attracts positive cations.
What is the positive electrode called?
Anode. Attract negative anions.
Rules for solution at the anode for electrolysis
If non metal is a halide (cl- Br-) then halide is made. If non metal is sulphate then oxygen is made because OH- ions form water which decomposes oxygen + hydrogen
Rules for solution at cathode in electrolysis
If metal cation is more reactive than hydrogen, metal stays in solution + hydrogen is made. If metal is less reactive than hydrogen, metal is made
OILRIG
Oxidation is loss. Reduction is gain (of electrons)
REDOX
A substance is being oxidised whilst the other substance is reduced
Half equations
If it’s being reduced the electrons are on left hand side of equation. If it’s oxidised electrons are on right hand side of equation
Reactivity series acronym to know of the element is more/less reactive than hydrogen
Please Stop Calling Me A Crazy Zebra Instead Try Learning How Copper Saves Gold
What happens at the cathode in copper sulphate solution? (Inert electrodes)
Copper is less reactive than hydrogen so copper metal is produced
What happens at the anode in copper sulphate solution? (Inert electrodes)
There aren’t any halide ions so oxygen + water are produced (you see bubbles of oxygen)
What happens in electrolysis of copper sulphate solution with copper electrodes instead?
The mass of anode decreases and mass of cathode increases. This is because copper is transferred from anode to cathode + pure copper is made at cathode.
How do you measure the electrodes change of mass in copper practical?
Weigh them before and after experiment + find difference. Make sure electrodes are dry.
